Such drug delivery devices have application where regular injection by persons without formal medical training occurs, i.e., patients. This is increasingly common amongst those having diabetes where self-treatment enables such persons to conduct effective management of their diabetes.
These circumstances set a number of requirements for drug delivery devices of this kind. The device must be robust in construction, yet easy to use in terms of the manipulation of the parts, understanding by a user of its operation and the delivery of the required dose of medicament. Dose setting must be easy and unambiguous. In the case of those with diabetes, many users will be physically infirm and may also have impaired vision requiring the drive mechanism to have low dispensing force and an easy to read dose setting display. In case of disposable devices, the device should be cheap to manufacture and easy to dispose of (preferably being suitable for recycling). To meet these requirements the number of parts required for assembling the device and the number of material types the device is made from need to be kept to a minimum.
User operated drug delivery devices and their methods of assembly are well known within the medical field.
Most prior art technologies have the disadvantage that the drug delivery devices comprise a two part housing, which weakens the mechanical stability of the device, e.g., between cartridge and drive mechanism, which may result in unsatisfactory user safety issues.
U.S. Pat. No. 5,226,895 discloses a syringe comprising a unitary housing for holding a container of liquid and a plunger rod having a non-cylindrical cross-section. The syringe further comprises a collar received within the housing having a non-cylindrical cross-section corresponding to the piston rod. The dose dial mechanism of the disclosed concept is mechanically engaged with the unitary housing.
WO9813085A1 discloses a needle-less injector device having a unitary housing, comprising a chamber for the drug to be applied, a liquid outlet, a dispensing member, an impacting member, a drive means, and a pressure sensor, where the chamber, the liquid outlet and the drive means are immobile with respect to the housing. This device does not comprise a dose dial mechanism.